Direct speciation of lead, zinc and antimony in fly ash from waste treatment facilities by XAFS spectroscopy

Abstract

It is important to understand the chemical states of heavy metals in solid waste from municipal incinerator (MSWI) fly ash as both the toxicity and behavior in the environment of heavy metals differ with their chemical states. In this study, direct speciation of lead, antimony and zinc in MSWI fly ash was conducted by XAFS spectroscopy. Three kinds of fly ash from continuous stoker-type MSWIs and a kind of fly ash from an ash melting plant (AMP) were investigated. XAFS measurements were carried out on beam line BL01B1 at SPring-8. The lead, zinc and antimony spectra were collected in fluorescence detection mode at room temperature with a Si (111) or Si (311) monochromator. According to Pb LIII-edge XANES spectra, lead was estimated to be predominantly PbCl2 in MSWI fly ashes and PbO in AMP fly ash. Zinc was estimated to be speciated predominantly as ZnCl2 in MSWI fly ashes and a mixture of 2ZnCO3·Zn(OH)2, ZnO and ZnS in AMP fly ash. Antimony K-edge XANES spectra indicated that Sb is five-valent in all the fly ashes.